JPH0581717U - Acceleration sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] One acceleration sensor can detect three-dimensional acceleration. [Structure] The elastic body 5 has radial bending portions 6 extending in three or more directions. A piezoelectric element 11 is provided on each flexible portion 6. The output voltage from the piezoelectric element 11 is compared by an amplifier of a detection circuit (not shown). By this comparison, it is possible to know the bending shape of the elastic body 5 (whether it is bent in an S shape, bent in a mountain shape, or bent in a valley shape), and the direction of acceleration can be detected. Further, the magnitude of acceleration can be detected from the magnitude of the difference between the compared output voltages.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to the structure of an acceleration sensor.

[0002]

[Prior Art]

 An example of a conventional acceleration sensor is shown in FIGS. 11 and 12. The acceleration sensor shown in FIG. 11 is compressed or pulled by the acceleration of the piezoelectric element 1 acting on the mass 3 (acts in the vertical direction in the figure). Therefore, the output voltage is extracted to detect the magnitude of the acceleration. To do.

In the acceleration sensor shown in FIG. 12, the piezoelectric element 1 receives a shearing force due to the acceleration acting on the mass 3 (acting in the vertical direction in the figure), and therefore the output voltage generated due to this shearing strain. The magnitude of acceleration is detected by.

These acceleration sensors only detect the magnitude of acceleration in the axial direction (vertical direction in the figure; direction of compression or tension with respect to the piezoelectric element 1). Therefore, when simultaneously detecting the acceleration in the left-right direction in the figure or in the direction orthogonal to the paper surface, a plurality of acceleration sensors had to be used in combination. By using the combination in this way, not only the magnitude of acceleration but also the direction can be detected.

[0005]

[Problems to be solved by the device]

 However, as described above, in order to detect not only the acceleration in the one-axis direction but also the acceleration in the two-axis or three-axis direction (two-dimensional or three-dimensional acceleration), it is necessary to combine a plurality of acceleration sensors. There has been a problem that the shape and size of the device increase and the manufacturing cost of the device also increases.

[0006]

[Means for Solving the Problems]

 The present invention solves the above-mentioned problems, and detects a plate-like elastic body whose ends are supported, a mass fixed to the center of the elastic body via an arm, and a flexure of the elastic body. It is characterized by comprising a plurality of strain sensors and a detection circuit for detecting the direction and magnitude of the acceleration acting on the mass based on the output signals from the strain sensors.

Further, in the acceleration sensor according to the present invention, the elastic body has radial bending portions extending in three or more directions, and the strain sensor is a piezoelectric element and is provided in each bending portion. The detection circuit may include an amplifier that compares the output voltage from each piezoelectric element.

[0008]

[Action]

 According to the present invention having the above-mentioned configuration, when acceleration acts in a direction parallel to the plate-like elastic body, a force based on the acceleration acts on the mass, and the joint between the arm and the elastic body is A moment proportional to the length is generated, and the elastic body bends in an S shape when viewed from the side. Based on the output signals from the respective strain sensors provided in the portions corresponding to the S-shaped peaks and valleys of the elastic body, the acceleration acting in either direction along the longitudinal direction of the elastic body Can be detected. Also, the magnitude of acceleration can be detected from the magnitude of the output signal. Further, when acceleration acts in a direction orthogonal to the plate-shaped elastic body, the elastic body bends in a mountain shape or a valley shape. Since it is possible to know whether it is mountain-shaped or valley-shaped by the output signal from the strain sensor, the direction of acceleration can be detected. Also, the magnitude of acceleration can be detected from the magnitude of the output signal.

If the elastic body has radial bending portions extending in three or more directions, when acceleration acts in a direction parallel to the elastic body, the direction parallel to the elastic body is two-dimensional. Can be detected. That is, by comparing the output voltage from the piezoelectric element, which is a strain sensor provided in three or more flexures, with the amplifier of the detection circuit, it is possible to accelerate in either direction within the plane elastic body and the plane. Can be detected. Further, the magnitude of acceleration is detected based on the magnitude of the difference between the output voltages compared. Therefore, in addition to the fact that the acceleration in the direction perpendicular to the elastic body can be detected as described above, the three-dimensional acceleration can be detected in total.

[0010]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. As shown in FIGS. 1 and 2, the plate-shaped elastic body 5 has a bending portion 6 extending radially in four directions. The ends of the flexible portions 6 are integrally fixed by a ring-shaped portion 7 and supported by the housing 8. The center of each bending portion 6 is integrally fixed, an arm 9 extending upward is fixed, and a mass 10 is fixed to the tip of the arm 9.

A piezoelectric element 11, which is a strain sensor, is provided on the four flexures 6. The piezoelectric element 11 detects the bending of the bending portion 6. That is, when the bending portion 6 bends in a mountain shape, the piezoelectric element 11 receives a tension, and when the bending portion 6 bends in a valley shape, the piezoelectric element 11 receives a compression and outputs positive and negative voltages. These outputs are taken out of the housing 8 by the lead wire 12 (one-dot chain line in FIG. 2) and input to the amplifier 13 of the detection circuit shown in FIG. 4 or 7.

The upper part of the housing 8 is sealed by a lid 15 to prevent dust from entering.

Next, the relationship between the direction of acceleration and the bending shape of the elastic body 5 is shown in FIGS. 3, 5, and 6. As shown in FIG. 3, when the acceleration is parallel to the elastic body 5 and acts in the right direction in the figure, a force acts on the mass 10 in the left direction, a moment is generated by the arm 9, and the elastic body 5 Has a lateral S-shape, and the S-shape has a mountain shape on the right and a valley shape on the left. On the contrary, when acceleration acts in the left direction in the figure in parallel with the elastic body 5, the left side of the elastic body 5 in the figure becomes a mountain shape and the right side becomes a valley shape. In this way, the bending shape (S-shape) of the elastic body 5 differs depending on whether the acceleration acts to the right or to the left. Then, the voltage output by the piezoelectric element 11 in the mountain-shaped portion due to the elastic body 5 bending in the S shape and the voltage output by the piezoelectric element 11 in the valley-shaped portion are opposite in positive and negative. Or the direction of the change of the voltage is opposite, so that the deflection shape (S shape) of the elastic body 5 is determined by comparing this with the amplifier 13. This makes it possible to detect in which direction parallel to the elastic body 5 the acceleration acts. Further, similarly to the conventional acceleration sensor, by calibrating the output voltage value of the amplifier 13 with respect to the known acceleration, the acceleration can be calculated based on the magnitude of the difference between the output voltages compared by the amplifier 13. The size can be detected.

Next, when an acceleration acts upward in the drawing in the thickness direction of the elastic body 5, a downward force is applied to the mass 10 as shown in FIG. As a result, the elastic body 5 is entirely bent in a valley shape. At this time, all the four piezoelectric elements are compressed and output voltages of the same sign.

On the other hand, when acceleration acts downward, a force acts upward on the mass 10 as shown in FIG. 6, so that the four piezoelectric elements output voltages of opposite signs. To do.

That is, as shown in FIG. 3, when acceleration is applied in the left-right direction in the drawing and in a direction orthogonal to the paper surface, as shown in FIG. 5, when acceleration is applied in the upward direction in the drawing, and As shown in FIG. 6, when acceleration is applied in the downward direction in the figure, the bending shapes of the elastic bodies are all different, and the difference in the bending shapes determines whether the force applied to each piezoelectric element 11 is a compressive force or a tensile force. Since they differ, it is possible to detect which direction the acceleration is in by comparing the output voltage from each piezoelectric element.

Next, a detection circuit for performing this detection is shown in FIG. 8 shows changes in the outputs A, B, C, D of the four amplifiers 13 used in the detection circuit of FIG.

As is apparent from FIG. 8, with respect to accelerations α and β in two directions parallel to and orthogonal to the elastic body 5 and accelerations γ in a direction orthogonal to these directions (the downward direction orthogonal to the paper surface is positive), The positive and negative voltages of the four output voltages are all different. In this way, the directions of the three-dimensional accelerations α, β, γ can be detected. Further, since the magnitude of the difference between the output voltages compared by the amplifier 13 corresponds to the magnitude of the acceleration acting at that time, the magnitude of the acceleration can also be detected.

The results shown in FIG. 8 above show the case where either acceleration α, β in the direction parallel to the elastic body 5 or acceleration γ in the direction orthogonal to the elastic body 5 acts independently. However, in practice, it is rare that they act alone, and one acceleration has these three-dimensional components. Therefore, the combined vector having the magnitudes of the accelerations α, β, γ in the three directions as components represents the actual acceleration.

As described above, it is possible to detect the accelerations α, β, γ in the three-axis directions and to detect the three-dimensional accelerations by using one acceleration sensor including one elastic body 5.

In the above embodiment, the ends of the four flexible portions 6 of the elastic body 5 are fixed by the ring-shaped portion 7. However, as shown in FIG. 9, each end is a free end. You can come.

Further, in the above embodiments, the elastic body 5 has been described as having four radial bending portions 6 which are orthogonal to each other. However, as shown in FIG. 10, three bending portions 6 are provided. It may be configured to have one. Of course, it is also possible to configure it as having five or more bending portions 6.

Further, the elastic body 5 can be formed into one elongated plate shape having two bending portions 6. In this case, the acceleration parallel to the elastic body 5 can be detected only one-dimensionally, but the acceleration in the direction orthogonal to the elastic body 5 can be detected, and the two-dimensional acceleration as a whole can be detected.

Further, in this embodiment, the end of the elastic body 5 is clamped in the groove formed in the housing 8 as shown in FIG. 1, and the rotation of the end is not allowed. However, it is also possible to adopt a configuration in which it is simply supported so that rotation is allowed. By supporting in this way, the bending of the elastic body can be further increased, and the tension or compression applied to the piezoelectric element can be further increased.

Furthermore, although the piezoelectric element 11 is used as the strain sensor in this embodiment, the strain sensor is not limited to the piezoelectric element 11, and other conventional strain sensors may be used.

Although the mass 10 is provided on the upper surface side of the elastic body 5, it may be provided on the back surface side of the elastic body 5.

Further, in the present embodiment, the arm 9 has a linear shape, but may have another suitable shape such as a three-dimensional curve (eg, spiral shape).

[0028]

[Effect of the device]

 As described above, according to the acceleration sensor of the present invention, by fixing the mass to the center of the plate-like elastic body whose ends are supported via the arm, the acceleration is accelerated in the direction parallel to the elastic body. When actuated, the elastic body bends in an S shape, and when acceleration acts in a direction orthogonal to the elastic body, it bends in a mountain shape or a valley shape. Therefore, at least two-dimensional acceleration is detected by detecting these deflections with a strain sensor. can do.

Further, the plate-like elastic body has radial bending portions extending in three or more directions, and a strain sensor is provided on each bending portion, which is excellent in that three-dimensional acceleration can be detected. It has an effect.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an acceleration sensor according to an embodiment of the present invention.

FIG. 2 is a plan view of an essential part of FIG.

FIG. 3 is a diagram showing bending when acceleration in the lateral direction in the figure is applied to the acceleration sensor of FIG.

4 is a diagram showing a detection circuit for detecting the direction and magnitude of acceleration in FIG.

FIG. 5 is a diagram showing bending when acceleration is applied upward to the acceleration sensor of FIG.

FIG. 6 is a diagram showing bending when downward acceleration is applied to the acceleration sensor of FIG.

FIG. 7 is a diagram showing a detection circuit for detecting the direction and magnitude of acceleration shown in FIGS. 3, 5 and 6;

8 is a diagram showing an output from each amplifier of the detection circuit of FIG. 7. FIG.

FIG. 9 is a plan view of an elastic body according to another embodiment.

FIG. 10 is a plan view of an elastic body according to still another embodiment.

FIG. 11 is a vertical cross-sectional view showing an acceleration sensor of a first conventional example.

FIG. 12 is a vertical sectional view showing an acceleration sensor of a second conventional example.

[Explanation of symbols]

 5 Elastic body 6 Bending part 9 Arm 10 Mass 11 Piezoelectric element (strain sensor) 12 Lead wire 13 Amplifier

Claims (2)

[Scope of utility model registration request] 1. A plate-shaped elastic body having supported end portions, a mass fixed to the center of the elastic body via an arm, a plurality of strain sensors for detecting bending of the elastic body, and the strain. An acceleration sensor, comprising: a detection circuit that detects a direction and a magnitude of acceleration acting on the mass based on an output signal from the sensor. 2. The elastic body has radial flexures extending in three or more directions, the strain sensor is a piezoelectric element and is provided in each flexure, and a detection circuit is provided from each piezoelectric element. The acceleration sensor according to claim 1, further comprising an amplifier that compares output voltages of the acceleration sensors.